In ZAR, there is a possibility to disable scan of certain partitioning schemes like GPT, LDM, md-RAID and others.
To do so use "Advanced configuration" setting available at startup.
However, the symptoms you describe points to some disk problems.
Might be worthwhile to examine SMART status on the drives, just in case.
Quite often, hanging on MD check means bad blocks. In case of bad blocks, it is recommended to create disk image file first. However, if for some reason it is not an option, you can configure ZAR to handle a device with bad sectors in Runtime control panel but you need to move the hard drive in question to the SATA port rather than using USB. Only direct connection via SATA allows data recovery software to control input/output operations reliably.